Re: [sv-bc] $unit::m or $root.m in module instance?

Brad, nested modules are explicitly excluded from the global
definitions name space.  The problem that I think Paul is concerned
about is if one has:

module nest;
endmodule

module top;
    module nest;
    endmodule

    // how do I create a global "nest" here instead
    // of the top.nest version?  Do I have to use a configuration?

endmodule


I don't think the current syntax allows any mechanism to
specify that.  Similarly, I don't think that just $root
or similar is sufficient since I could easily add another
level of nesting and then want to talk about the "nest"
in my parent scope.

We likely need to allow general hierarchical names in the
syntax and have a semantic restriction that one can only
create instances of modules in scopes in scopes that are
lexically outwards from the instantiating scope.

Similar issues in terms of rebinding instances to other modules
will occur in configurations.  Imagine if you had some nesting
and wanted to configure a deeper instance to "top.nest";  I
don't think the current syntax would allow that.  We could
define that configurations have to find the module declaration
based on the nested location of the instance, but then the
reverse problem will still exist (how to configure a nested
instance to the one in the definitions space).

If we don't deal with this, we'll have to live with
much simpler instantiation relationships.  The current
syntax effectively enforces the restrictions and I am
not convinced that I really want to extend all of this,
but we need to make an intentional decision.  If we do
extend all of this, we need to be pretty careful about
how naming and other relationships are handled.

Gord



Brad Pierce wrote:
> Module names are in a global definitions name space, not in some
> particular $unit.  But to bind instances to different source
> descriptions, a configuration can be used.  
> 
> Should 
> 
>       topmodule_identifier ::= identifier
> 
> be
> 
>       topmodule_identifier ::= [ $root ] | identifier
> 
> ?
> 
> -- Brad
> 
> 
> -----Original Message-----
> From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of Paul
> Graham
> Sent: Wednesday, October 11, 2006 6:04 PM
> To: sv-bc@eda.org
> Subject: [sv-bc] $unit::m or $root.m in module instance?
> 
> It might be useful, in the presence of nested modules, to specify a
> module name in a module instantiation using $unit or $root:
> 
>     module top();
>         $unit::m1 u1();
> 	$root.m2 u2();
>     endmodule
> 
> The lrm says that the module name in a module_instantiation has to be an
> identifier.  This rules out using $unit::<id> and $root.<id> as module
> names.  I wonder if this restriction is intentional.
> 
> Paul
> 
> 

-- 
--------------------------------------------------------------------
Gordon Vreugdenhil                                503-685-0808
Model Technology (Mentor Graphics)                gordonv@model.com